ChangeTransform

This Transition captures scale and rotation for Views before and after the
scene change and animates those changes during the transition.
A change in parent is handled as well by capturing the transforms from
the parent before and after the scene change and animating those during the
transition.

Subclasses must implement this method. The method should only be called by the
transition system; it is not intended to be called from external classes.

Parameters

transitionValues

TransitionValues: The holder for any values that the Transition
wishes to store. Values are stored in the values field
of this TransitionValues object and are keyed from
a String value. For example, to store a view's rotation value,
a transition might call
transitionValues.values.put("appname:transitionname:rotation",
view.getRotation()). The target view will already be stored
in
the transitionValues structure when this method is called.

Subclasses must implement this method. The method should only be called by the
transition system; it is not intended to be called from external classes.

Parameters

transitionValues

TransitionValues: The holder for any values that the Transition
wishes to store. Values are stored in the values field
of this TransitionValues object and are keyed from
a String value. For example, to store a view's rotation value,
a transition might call
transitionValues.values.put("appname:transitionname:rotation",
view.getRotation()). The target view will already be stored
in
the transitionValues structure when this method is called.

createAnimator

This method creates an animation that will be run for this transition
given the information in the startValues and endValues structures captured
earlier for the start and end scenes. Subclasses of Transition should override
this method. The method should only be called by the transition system; it is
not intended to be called from external classes.

This method is called by the transition's parent (all the way up to the
topmost Transition in the hierarchy) with the sceneRoot and start/end
values that the transition may need to set up initial target values
and construct an appropriate animation. For example, if an overall
Transition is a TransitionSet consisting of several
child transitions in sequence, then some of the child transitions may
want to set initial values on target views prior to the overall
Transition commencing, to put them in an appropriate state for the
delay between that start and the child Transition start time. For
example, a transition that fades an item in may wish to set the starting
alpha value to 0, to avoid it blinking in prior to the transition
actually starting the animation. This is necessary because the scene
change that triggers the Transition will automatically set the end-scene
on all target views, so a Transition that wants to animate from a
different value should set that value prior to returning from this method.

Additionally, a Transition can perform logic to determine whether
the transition needs to run on the given target and start/end values.
For example, a transition that resizes objects on the screen may wish
to avoid running for views which are not present in either the start
or end scenes.

If there is an animator created and returned from this method, the
transition mechanism will apply any applicable duration, startDelay,
and interpolator to that animation and start it. A return value of
null indicates that no animation should run. The default
implementation returns null.

The method is called for every applicable target object, which is
stored in the view field.

Parameters

sceneRoot

ViewGroup: The root of the transition hierarchy.

startValues

TransitionValues: The values for a specific target in the start scene.

getReparent

Returns whether parent changes will be tracked by the ChangeTransform. If parent
changes are tracked, then the transform will adjust to the transforms of the
different parents. If they aren't tracked, only the transforms of the transitioning
view will be tracked. Default is true.

getReparentWithOverlay

Returns whether changes to parent should use an overlay or not. When the parent
change doesn't use an overlay, it affects the transforms of the child. The
default value is true.

Note: when Overlays are not used when a parent changes, a view can be clipped when
it moves outside the bounds of its parent. Setting
setClipChildren(boolean) and
setClipToPadding(boolean) can help. Also, when
Overlays are not used and the parent is animating its location, the position of the
child view will be relative to its parent's final position, so it may appear to "jump"
at the beginning.

Returns

boolean

true when a changed parent should execute the transition
inside the scene root's overlay or false if a parent change only
affects the transform of the transitioning view.

getTransitionProperties

Returns the set of property names used stored in the TransitionValues
object passed into captureStartValues(TransitionValues) that
this transition cares about for the purposes of canceling overlapping animations.
When any transition is started on a given scene root, all transitions
currently running on that same scene root are checked to see whether the
properties on which they based their animations agree with the end values of
the same properties in the new transition. If the end values are not equal,
then the old animation is canceled since the new transition will start a new
animation to these new values. If the values are equal, the old animation is
allowed to continue and no new animation is started for that transition.

A transition does not need to override this method. However, not doing so
will mean that the cancellation logic outlined in the previous paragraph
will be skipped for that transition, possibly leading to artifacts as
old transitions and new transitions on the same targets run in parallel,
animating views toward potentially different end values.

Returns

String[]

An array of property names as described in the class documentation for
TransitionValues. The default implementation returns null.

setReparent

Sets whether parent changes will be tracked by the ChangeTransform. If parent
changes are tracked, then the transform will adjust to the transforms of the
different parents. If they aren't tracked, only the transforms of the transitioning
view will be tracked. Default is true.

Parameters

reparent

boolean: Set to true to track parent changes or false to only track changes
of the transitioning view without considering the parent change.

setReparentWithOverlay

Sets whether changes to parent should use an overlay or not. When the parent
change doesn't use an overlay, it affects the transforms of the child. The
default value is true.

Note: when Overlays are not used when a parent changes, a view can be clipped when
it moves outside the bounds of its parent. Setting
setClipChildren(boolean) and
setClipToPadding(boolean) can help. Also, when
Overlays are not used and the parent is animating its location, the position of the
child view will be relative to its parent's final position, so it may appear to "jump"
at the beginning.

Parameters

reparentWithOverlay

boolean: true when a changed parent should execute the
transition inside the scene root's overlay or false
if a parent change only affects the transform of the
transitioning view.